This application is a 371 of PCT/EP98/07123 filed Nov. 9, 1998.
The invention concerns a composite sliding bearing material, with a hard metal support layer and a metal sliding layer roll-bonded onto the support layer and made from an aluminum alloy with 10 to 25 mass % tin and with copper and nickel additives which is in direct contact with the sliding partner. The sliding layer has no additional, e.g. galvanically applied, sliding layer.
A sliding bearing material of this kind is disclosed e.g. in DE 40 04 703 A1. The single embodiment describes an aluminum alloy with a composition of AlSn10Ni2Mn1Cu0.5, wherein lead can also be added instead of tin. Aluminum alloys of this kind which are used as sliding bearing material require a xe2x80x9csoft phasexe2x80x9d in the form of a tin or lead precipitate to guarantee good emergency running properties for a bearing produced from this sliding bearing material. Hard contaminating particles or abrasions are accepted by or embedded in this soft phase. The soft phase can also adjust to geometrical conditions. The soft phase of tin, which does not dissolve in aluminum, is received in the matrix-forming aluminum in the form of block-like precipitates.
Copper can be added to increase the stability of the aluminum matrix. Copper and aluminum form inter-metallic phases, so-called hard substance phases such as Al2Cu and finely distributed precursors thereof which increase the rigidity of the aluminum matrix when present as finely distributed precipitates (xe2x89xa61xcexcm). This increases the stability under load and fatigue resistance of a sliding bearing material produced from the alloy. An aluminum alloy AlSn15Cu2 of this kind has been disclosed under the trade name KS 985.3 by the assignee. This alloy has excellent tribological properties but is inadequate under extreme loads such as e.g. occur in connecting rod bearings in modern internal combustion engines.
Improvements have been attempted in the aluminum alloy disclosed in DE 40 04 701 A1 by adding manganese and nickel to increase the proportion of hard substance phases, in particular, according to this document, in the region of the tin precipitates to improve bonding of the tin precipitates in the aluminum matrix due to the affinity of tin for nickel and manganese.
A certain proportion of hard substance phases or precipitates is believed to have a positive effect on the wear resistance in that the hard substance phases on the surface effect fine abrasion of the sliding partner, e.g. of the crank shaft, to abrade roughness peaks in the steel sliding partner. The hard substance phases also increase the stability of the bearing material under load.
Increasing the proportion of inter-metallic hard substance phases also causes problems with respect to fatigue resistance and manufacture. Shaping, in particular during cold-plating of the aluminum alloy on steel requiring a pass having approximately 50% shaping, thereby produces cracks.
DE 37 27 591 A1 discloses a multiple layer sliding bearing substance comprising an intermediate layer of AlSn6CuNi between a steel supporting base and a galvanically disposed sliding layer having a thickness between 5 and 50 xcexcm.
It is the underlying purpose of the present invention to improve an alloy of the above mentioned kind such that its stability under load is better than that of conventional aluminum-tin-copper or aluminum-tin-copper-nickel-alloys and which has improved plasticity, in particular, plateability.